The invention relates to a magnetic circuit, for an electro-magnet, comprising a massive cylindrical core adapted to receive a winding and of which a first extremity has a surface of association which is fixed by electric welding against a bearing surface of a massive magnet pot element having arms in "L" shape or "U" shape such that the axis of the said core is perpendicular to the bearing surface, whilst a first polar surface disposed on a second extremity opposite to the first is disposed at a predetermined axial distance from a second polar surface placed at the extremity of one of the arms.
Such magnet pot elements are used to a great extent in continuous current or alternating current relays as well as in mixed excition relays which can receive windings fed either with continuous current or with alternating current.
Among the problems which are frequently met with in massive magnetic pot elements intended for relays there are those of the proper orientation of the axis of the core, and of the respecting of the distance mentioned above, and for the mixed supply pot elements that of producing them economically.
Failure to respect the geometry during manufacture, or simply making compromises results, in effect, in the absence of a correcting operation and above all in electro-magnets wherein economy of copper has been sought, in deteriorations in the forces of attraction for pulling the armature and/or in variation of the forces maintaining the armature in its working position.
It is thus necessary to give the core and the arms a perfect orientation and a precise length, and to reduce the number of correcting operations which may be required.